Multi-level solid electrolyte, preparation method thereof, electrochemical device and electronic equipment

Abstract

The invention relates to the technical field of electrochemical energy storage, in particular to a multi-level solid electrolyte, a preparation method thereof, an electrochemical device and electronic equipment. The multi-level solid electrolyte comprises an interface stabilizing layer, an inorganic electrolyte compact layer and a high-pressure-resistant interface layer which are sequentially compounded, the ionic conductivity of the inorganic electrolyte compact layer is larger than 10 <-4 > S / cm, the interface stabilizing layer comprises a first polymer and chloride, and the high-pressure-resistant interface layer comprises a second polymer and high-pressure-resistant inorganic filler. And the oxygenolysis voltage of the high-voltage-resistant interface layer is greater than 4.5 V. The multi-level solid electrolyte provided by the invention has high ionic conductivity, excellent lithium dendrite inhibition capability and good interface stability at the same time.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, and in particular to a multi-level solid electrolyte, its preparation method, electrochemical device, and electronic device. Background Technology

[0002] Solid-state lithium batteries are considered strong candidates for next-generation high-energy-density, high-safety energy storage devices. Solid-state electrolytes are the core material, requiring high ionic conductivity, excellent mechanical strength (to suppress lithium dendrite growth), good interfacial stability, and a wide electrochemical window. However, existing single solid-state electrolyte materials are insufficient to meet these requirements. Polymer electrolytes (such as PEO-based electrolytes) offer good flexibility and interfacial contact, but suffer from low room-temperature ionic conductivity and insufficient mechanical strength, failing to effectively block lithium dendrite formation. Inorganic solid-state electrolytes (such as LLZO, LATP, and sulfides) have high ionic conductivity and high mechanical strength, but are hard and brittle, exhibiting poor solid-solid interface contact with the electrode, and are sensitive to water / oxygen in the air (especially sulfides), making them difficult to process.

[0003] While simply mixing polymers with inorganic electrolytes to prepare composite electrolytes can leverage the strengths of different materials, it often suffers from problems such as uneven distribution and agglomeration of inorganic fillers, leading to discontinuous ion transport pathways and limited performance improvement. Therefore, developing a multilayer solid-state electrolyte with a rational structural design that can synergistically utilize the advantages of different materials is crucial. Summary of the Invention

[0004] This invention provides a multi-level solid electrolyte that simultaneously possesses high ionic conductivity, excellent lithium dendrite suppression capability, and good interface stability.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A multi-layer solid electrolyte comprises, sequentially stacked, an interface stabilizing layer, an inorganic electrolyte dense layer, and a high-voltage resistant interface layer, wherein the ionic conductivity of the inorganic electrolyte dense layer is greater than 10. -4 S / cm, the interface stabilizing layer comprises a first polymer and a chloride, the high-pressure resistant interface layer comprises a second polymer and a high-pressure resistant inorganic filler, and the oxidative decomposition voltage of the high-pressure resistant interface layer is greater than 4.5V.

[0006] In some embodiments, the chloride includes at least one of LiCl, MgCl2, SnCl2, AlCl3, InCl3, SiCl4, and SnCl4.

[0007] In some embodiments, the first polymer includes at least one of polyvinylidene fluoride-hexafluoropropylene and polyethylene oxide.

[0008] In some embodiments, the inorganic electrolyte dense layer includes at least one of garnet-type, sodium superionic conductor-type, sulfide-type, and halide-type inorganic solid electrolytes.

[0009] In some embodiments, the high-pressure resistant inorganic filler includes at least one of LLZO, LATP, MgF2, and AlF3.

[0010] In some embodiments, the second polymer includes at least one of polyvinylidene fluoride, polyacrylonitrile, polycarbonate, and polyphosphate.

[0011] In some embodiments, the thickness of the interface stabilizing layer is 1-10 μm; And / or, the thickness of the inorganic electrolyte dense layer is 10-50 μm; And / or the thickness of the high-pressure resistant interface layer is 5-20 μm.

[0012] This invention also provides a method for preparing a multi-level solid electrolyte, which includes the following preparation steps: Step 1: Mix the second polymer and the high-pressure resistant inorganic filler with the solvent evenly to obtain a high-pressure resistant slurry. Coat the high-pressure resistant slurry onto an inert substrate and dry it to obtain a high-pressure resistant interface layer. Step 2: Hot-press the high-pressure resistant interface layer and the inorganic electrolyte dense layer together to obtain a composite film; Step 3: Dissolve the first polymer and chloride in a solvent to make a slurry, coat the slurry onto the surface of the inorganic electrolyte dense layer of the composite membrane, dry and hot press to obtain a multi-layer solid electrolyte.

[0013] The present invention also provides an electrochemical device comprising a positive electrode, a negative electrode, and a multi-level solid electrolyte disposed between the positive electrode and the negative electrode. The multi-level solid electrolyte is the multi-level solid electrolyte described above or the multi-level solid electrolyte prepared by the above preparation method. The interface stabilizing layer of the multi-level solid electrolyte is located on the side closer to the negative electrode, and the high-voltage resistant interface layer of the multi-level solid electrolyte is located on the side closer to the positive electrode.

[0014] The present invention also provides an electronic device comprising the above-described electrochemical device.

[0015] The beneficial effects of this invention are: The multi-layered solid-state electrolyte of this invention is composed of a sequentially composited interface stabilizing layer, an inorganic electrolyte dense layer, and a high-voltage resistant interface layer. This distributes the three major functions of interface stabilization, dendrite blocking, and interface contact to different layers, achieving complementary advantages and synergistic effects in material performance and overcoming the performance bottlenecks of single materials or simple composite materials. The dense, high-modulus inorganic layer in the middle effectively physically blocks lithium dendrites, preventing battery short circuits. The stable anode interface layer and the good cathode interface layer together reduce interface impedance, suppress side reactions, and extend battery cycle life. This electrolyte allows the use of high-capacity lithium metal anode and high-voltage cathode materials, thereby significantly improving the energy density of all-solid-state batteries.

[0016] The interface stabilizing layer contacts the lithium metal anode, allowing the chloride component to effectively lower the lithium-ion diffusion barrier and induce uniform lithium nucleation and deposition. Furthermore, the interface stabilizing layer's stable chemical properties enable it to spontaneously form a stable, LiCl-rich solid electrolyte interface film with the lithium metal, suppressing side reactions. The dense inorganic electrolyte layer, acting as a dendrite barrier, possesses a high Young's modulus (>6 GPa), providing a strong mechanical barrier for lithium dendrite growth and effectively inhibiting dendrite penetration into the electrolyte. This dense inorganic electrolyte layer also exhibits high ionic conductivity, ensuring rapid lithium-ion passage. The high-voltage resistant interface layer contacts the high-voltage cathode material (such as NCM811, lithium cobalt oxide, and lithium-rich manganese-based materials), ensuring high voltage compatibility and improving interface contact. The second polymer matrix and the high-voltage resistant inorganic filler have a wide electrochemical window (>4.5 V vs. Li / Li⁺), preventing oxidative decomposition under high voltage. The polymer's flexibility adapts to volume changes in the cathode material during charging and discharging, providing good solid-solid interface contact and reducing interface impedance. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0018] Figure 1 This is a comparison chart of the critical current density of batteries in Embodiment 1 and Comparative Example 1 of the present invention; Figure 2 This is a comparison chart of the voltage-time curves of the batteries in Embodiment 1 and Comparative Example 1 during the cycling process of the present invention; Figure 3 This is the XPS pattern of an SEI formed on a lithium metal surface in Example 1 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. The embodiments described below are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art in conjunction with the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed; where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0020] In the description of this invention, the term "and / or" describes the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following associated objects have an "or" relationship.

[0021] In the description of this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0022] It should be understood that the weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope of this invention. Specifically, the weights mentioned in the embodiments of this invention can be well-known units of mass in the chemical industry, such as μg, mg, g, and kg.

[0023] Furthermore, unless the context explicitly uses it otherwise, the singular form of a word should be understood as including the plural form of that word. The terms "comprising" or "having" are intended to specify the presence of a feature, quantity, step, operation, element, part, or combination thereof, but are not intended to exclude the presence or possible addition of one or more other features, quantities, steps, operations, elements, parts, or combinations thereof.

[0024] This invention provides a multi-layer solid electrolyte comprising, sequentially stacked, an interface stabilizing layer, an inorganic electrolyte dense layer, and a high-voltage resistant interface layer, wherein the inorganic electrolyte dense layer has an ionic conductivity greater than 10. -4S / cm, the interface stabilizing layer comprises a first polymer and a chloride, the high-pressure resistant interface layer comprises a second polymer and a high-pressure resistant inorganic filler, and the oxidative decomposition voltage of the high-pressure resistant interface layer is greater than 4.5V.

[0025] The multi-layered solid-state electrolyte of this invention is composed of a sequentially composited interface stabilizing layer, an inorganic electrolyte dense layer, and a high-voltage resistant interface layer. This distributes the three major functions of interface stabilization, dendrite blocking, and interface contact to different layers, achieving complementary advantages and synergistic effects in material performance and overcoming the performance bottlenecks of single materials or simple composite materials. The dense, high-modulus inorganic layer in the middle effectively physically blocks lithium dendrites, preventing battery short circuits. The stable anode interface layer and the good cathode interface layer together reduce interface impedance, suppress side reactions, and extend battery cycle life. This electrolyte allows the use of high-capacity lithium metal anode and high-voltage cathode materials, thereby significantly improving the energy density of all-solid-state batteries.

[0026] The interface stabilizing layer contacts the lithium metal anode, allowing the chloride component to effectively lower the lithium-ion diffusion barrier and induce uniform lithium nucleation and deposition. Furthermore, the interface stabilizing layer's stable chemical properties enable it to spontaneously form a stable, LiCl-rich solid electrolyte interface film with the lithium metal, suppressing side reactions. The dense inorganic electrolyte layer, acting as a dendrite barrier, possesses a high Young's modulus (>6 GPa), providing a strong mechanical barrier for lithium dendrite growth and effectively inhibiting dendrite penetration into the electrolyte. This dense inorganic electrolyte layer also exhibits high ionic conductivity, ensuring rapid lithium-ion passage. The high-voltage resistant interface layer contacts the high-voltage cathode material (such as NCM811, lithium cobalt oxide, and lithium-rich manganese-based materials), ensuring high voltage compatibility and improving interface contact. The second polymer matrix and the high-voltage resistant inorganic filler have a wide electrochemical window (>4.5 V vs. Li / Li⁺), preventing oxidative decomposition under high voltage. The polymer's flexibility adapts to volume changes in the cathode material during charging and discharging, providing good solid-solid interface contact and reducing interface impedance.

[0027] In some embodiments, the chloride includes at least one of LiCl, MgCl2, SnCl2, AlCl3, InCl3, SiCl4, and SnCl4.

[0028] The aforementioned chlorides possess high lithium-ion affinity or can participate in the in-situ generation of highly ion-conducting interfacial phases, effectively reducing the diffusion barrier of lithium ions at the interface and promoting uniform lithium-ion transport. On the other hand, these chlorides can undergo reduction reactions on the lithium metal surface, generating in-situ nanoparticles with high surface energy. These nanoparticles serve as lithium nucleation sites, guiding uniform lithium-ion deposition and suppressing dendrite nucleation.

[0029] When the aforementioned chlorides come into contact with lithium metal, they readily undergo an interfacial reaction, forming a LiCl-rich solid electrolyte interphase (SEI) film in situ. LiCl possesses high interfacial energy, low electronic conductivity, and good chemical stability, effectively preventing the continuous decomposition of the electrolyte, enhancing interfacial stability, and suppressing side reactions.

[0030] In summary, by introducing specific chlorides into the interface stabilization layer, not only is the ionic conductivity and electrochemical stability of the lithium metal anode interface significantly improved, but also the lithium deposition behavior is effectively regulated, thereby synergistically enhancing the cycle performance, safety, and energy density of the multilayer solid electrolyte.

[0031] In some embodiments, the first polymer includes at least one of polyvinylidene fluoride-hexafluoropropylene and polyethylene oxide.

[0032] Polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) possesses a high dielectric constant, good electrochemical stability, and relative inertness to lithium metal, effectively reducing side reactions with the lithium anode and improving long-term interfacial stability. While polyethylene oxide (PEO) exhibits limited stability at high voltages, it performs well in low-potential environments near the lithium metal anode, and its ether oxygen groups can coordinate with lithium ions, promoting lithium salt dissociation and ion migration.

[0033] PEO itself possesses a certain lithium-ion conductivity. Although its conductivity is low at room temperature, when combined with chlorides, it can form Lewis acid-base interactions, weakening polymer crystallinity and increasing the proportion of amorphous regions, thereby significantly improving room-temperature ionic conductivity. While PVDF-HFP has low intrinsic ionic conductivity, its porous microstructure can indirectly promote lithium-ion migration by absorbing solvents or trace amounts of electrolyte or forming ion transport channels with chlorides. Therefore, using PVDF-HFP and / or PEO as the first polymer in combination with chlorides can synergistically improve ionic conductivity.

[0034] Both PVDF-HFP and PEO have excellent film-forming properties and flexibility. Using them as polymer matrices for the interface stabilization layer can enable the interface stabilization layer to adhere tightly to the surface of the lithium metal anode, effectively mitigating the volume changes caused by lithium deposition / stripping during charging and discharging, maintaining stable solid-solid interface contact, and reducing interface impedance.

[0035] Both the strongly polar groups of PVDF-HFP and the ether oxygen groups of PEO can form coordination or hydrogen bonding with metal chlorides, inhibiting their aggregation or hydrolysis and achieving uniform dispersion at the nanoscale, thereby giving full play to the role of chlorides in interface regulation and SEI construction.

[0036] In summary, using PVDF-HFP and / or PEO as the first polymer in the interface stabilization layer not only ensures stable and low-impedance contact with the lithium metal anode, but also significantly improves the interfacial ion transport kinetics and lithium deposition uniformity through synergistic effects with chloride, which is beneficial to improving battery safety and cycle life.

[0037] In some embodiments, the inorganic electrolyte dense layer includes at least one of garnet-type, sodium superionic conductor-type, sulfide-type, and halide-type inorganic solid electrolytes.

[0038] All four types of inorganic electrolytes mentioned above have an ionic conductivity greater than 10 at room temperature. -4 The high Young's modulus (typically >6 GPa, garnet type up to 150-200 GPa) effectively suppresses lithium dendrite penetration, preventing internal short circuits and significantly improving safety. Furthermore, the high ionic conductivity and wide electrochemical window of the inorganic electrolyte, along with its dense layer, allow for the use of high-capacity lithium metal anodes and high-voltage cathodes (such as NCM811 and lithium-rich manganese-based electrodes), which is beneficial for increasing battery energy density.

[0039] The dense inorganic electrolyte layer, serving as the core functional framework, is sandwiched between flexible polymer interface layers. It utilizes its high modulus to prevent dendrite formation and mitigates poor interfacial contact caused by the brittleness of the polymer through the upper and lower interface layers. In particular, when using inorganic materials unstable to lithium, the interface stabilizing layer can form a protective SEI in situ, blocking side reactions and thus expanding the application boundaries of previously limited materials.

[0040] Specifically, garnet-type inorganic solid electrolytes can be LLZO, sodium superionic conductor-type inorganic solid electrolytes can be LATP, and sulfide-type inorganic solid electrolytes can be LPSC and LGPS.

[0041] In some embodiments, the high-pressure resistant inorganic filler includes at least one of LLZO, LATP, MgF2, and AlF3.

[0042] LLZO (garnet-type lithium lanthanum zirconium oxide) and LATP (sodium superionic conductor lithium titanium aluminum phosphate) have wide electrochemical windows (>4.5 V vs. Li). + (Li), especially LLZO, which can be stable up to 6 V and is not easily oxidized and decomposed at high voltage; MgF2 and AlF3 are typical wide bandgap, high stability fluorides with extremely strong oxidation resistance and chemical inertness. They maintain structural stability even at high potentials of 4.5-5.0 V and can effectively suppress the oxidation side reactions of electrolyte at the positive electrode interface.

[0043] The aforementioned inorganic filler, when combined with the second polymer, can form an interface layer on the positive electrode surface that combines ion conductivity and electronic insulation. LLZO / LATP can provide additional lithium-ion transport channels; MgF2 / AlF3 nanoparticles can induce the reaction of fluorine sources generated by lithium salts, residual solvents, or side reactions during battery operation with Li. + Highly stable LiF is generated in situ on its surface, thus constructing an excellent CEI layer, which helps passivate the cathode surface and reduce transition metal dissolution and electrolyte decomposition. Therefore, the selection of the above-mentioned inorganic filler is beneficial for constructing a stable, low-impedance cathode-electrolyte interface.

[0044] High-nickel or lithium-rich cathodes undergo significant volume changes (>5%) during charge and discharge, which can easily lead to debonding between the rigid inorganic electrolyte and the cathode. This invention, however, uniformly disperses the aforementioned high-voltage resistant inorganic filler within a flexible second polymer matrix. This preserves the electrochemical stability of the inorganic material while utilizing the elastic buffering effect of the polymer to maintain a tight solid-solid interface contact, reducing interfacial impedance and improving cycle stability.

[0045] Under high voltage, polymer electrolytes (such as PEO) are prone to chain breakage and oxidation gas generation. The present invention introduces fluorides such as MgF2 and AlF3 to capture active oxygen species or HF (if trace moisture is present), reduce interfacial corrosion and gas generation, and improve battery safety and cycle life.

[0046] LLZO, LATP, MgF2, and AlF3 are all high-melting-point, non-flammable inorganic materials. Their addition significantly improves the thermal stability of the high-voltage interface layer, avoids polymer softening failure at high temperatures, and thus enhances the thermal safety performance of the full battery.

[0047] In summary, by selecting specific high-voltage resistant inorganic fillers, the high-voltage resistant interface layer can simultaneously possess chemical stability, ion transport capability, interface adhesion, and thermal safety at high potentials. This effectively solves the problem of interface incompatibility between high-voltage cathodes and solid electrolytes, which is beneficial for improving battery energy density and lifespan.

[0048] In some embodiments, the second polymer includes at least one of polyvinylidene fluoride, polyacrylonitrile, polycarbonate, and polyphosphate.

[0049] Polyvinylidene fluoride (PVDF) possesses strong CF bonds, a wide electrochemical window, and structural stability at high nickel cathode operating potentials, making it less prone to chain breakage or gas generation. Polyacrylonitrile (PAN) contains strongly polar –C≡N groups, which not only enhance the dielectric constant and promote lithium salt dissociation, but its conjugated structure also provides excellent oxidation resistance, allowing stable operation above 4.6V. Polycarbonate exhibits high oxidation stability (>4.5V) and good flexibility, which is beneficial for interface buffering. Polyphosphate contains strongly polar groups, providing not only a wide electrochemical window but also self-flame retardancy and HF capture capabilities, further enhancing battery safety. These polymers are not easily oxidized at high potentials, thus ensuring the long-term stability of the high-voltage interface layer.

[0050] The high dielectric constants of PVDF and PAN can effectively shield the Coulomb attraction between lithium salt cations and anions, promoting the dissociation of lithium salts such as LiTFSI and LiFSI, and increasing the number of free Li. + Concentration; the P=O group in polyphosphate is a strong Lewis base and can react with Li. + Coordination forms dynamic coordination-dissociation channels, which is beneficial for lithium ion migration; at room temperature, these polymer matrices can also maintain relatively high interfacial ionic conductivity, significantly reducing the cathode / electrolyte interface impedance.

[0051] Polymers containing polar groups, such as PVDF and PAN, can form hydrogen bonds or dipole-dipole interactions with the surface of inorganic fillers, effectively inhibiting the agglomeration of high-pressure resistant inorganic fillers and ensuring a continuous ion transport network and stable mechanical support.

[0052] High-capacity cathode materials (such as NCM811 and lithium-rich manganese-based materials) undergo significant lattice expansion / contraction during charging and discharging. This invention employs a second polymer of the aforementioned types. The elasticity and ductility of the second polymer can buffer stress, prevent the rigid inorganic electrolyte from debonding from the cathode particles, maintain a tight solid-solid contact, avoid a sharp increase in interface impedance during cycling, suppress the generation of microcracks, and extend the battery cycle life.

[0053] By selecting the aforementioned types of second polymers, it is beneficial to form a high-voltage resistant interface layer with high voltage stability, good ion conductivity, excellent interface adhesion, and thermal safety, thereby suppressing interface side reactions, impedance growth, and structural degradation, thus supporting the long-cycle stable operation of high-energy-density all-solid-state lithium batteries.

[0054] In some embodiments, the thickness of the interface stabilizing layer is 1-10 μm, the thickness of the inorganic electrolyte dense layer is 10-50 μm, and the thickness of the high-voltage resistant interface layer is 5-20 μm.

[0055] This invention also provides a method for preparing a multi-level solid electrolyte, which includes the following preparation steps: Step 1: Mix the second polymer and the high-pressure resistant inorganic filler with the solvent evenly to obtain a high-pressure resistant slurry. Coat the high-pressure resistant slurry onto an inert substrate and dry it to obtain a high-pressure resistant interface layer. Step 2: Hot-press the high-pressure resistant interface layer and the inorganic electrolyte dense layer together to obtain a composite film; Step 3: Dissolve the first polymer and chloride in a solvent to make a slurry, coat the slurry onto the surface of the inorganic electrolyte dense layer of the composite membrane, dry and hot press to obtain a multi-layer solid electrolyte.

[0056] Specifically, the inorganic electrolyte dense layer can be prepared by purchasing commercially available inorganic electrolyte films, or by the following method: inorganic electrolyte powder is shaped by dry or wet methods and sintered at an appropriate temperature to form a dense ceramic sheet, thus obtaining the inorganic electrolyte dense layer.

[0057] The present invention also provides an electrochemical device comprising a positive electrode, a negative electrode, and a multi-level solid electrolyte disposed between the positive electrode and the negative electrode. The multi-level solid electrolyte is the multi-level solid electrolyte described above or the multi-level solid electrolyte prepared by the above preparation method. The interface stabilizing layer of the multi-level solid electrolyte is located on the side closer to the negative electrode, and the high-voltage resistant interface layer of the multi-level solid electrolyte is located on the side closer to the positive electrode.

[0058] In some embodiments, the negative electrode is a lithium metal negative electrode or a lithium alloy negative electrode.

[0059] In some embodiments, the positive electrode comprises a high-voltage positive electrode material, and the operating voltage of the positive electrode is greater than or equal to 4.3 V (vs. Li / Li⁺).

[0060] The present invention also provides an electronic device comprising the above-described electrochemical device.

[0061] To enable those skilled in the art to clearly understand the above-described implementation details and operations of the present invention, and to demonstrate the significant advancements in the performance of the embodiments of the present invention, the following examples illustrate the above technical solutions.

[0062] Example 1 A method for preparing a multi-level solid electrolyte includes the following preparation steps: Step 1: Prepare a high-pressure resistant interface layer: Lithium bis(fluorosulfonyl)imide (LiFSI) and PVDF were dissolved in triethyl phosphate (TEP) and stirred until homogeneous. The mass ratio of lithium bis(fluorosulfonyl)imide, PVDF and triethyl phosphate was 1:1.5:40. Then, nano LLZO powder was added and ball-milled to mix evenly to obtain a high-pressure resistant slurry. The mass of nano LLZO powder accounted for 15 wt% of the total mass of the high-pressure resistant slurry. The high-pressure resistant slurry was cast into a film and dried to obtain a thin film with a thickness of 15 μm, namely the high-pressure resistant interface layer. Step 2: Dense inorganic electrolyte layer. This layer uses commercially available LLZO ceramic sheets with a thickness of 50 μm. The ionic conductivity of the dense inorganic electrolyte layer is greater than 10. -4 S / cm; Step 3: Align and bond the high-pressure resistant interface layer obtained in Step 1 and the inorganic electrolyte dense layer obtained in Step 2, and hot press them at 80℃ and 10 MPa for 5 minutes to obtain a composite membrane. Step 4: Prepare the interface stabilizing layer: PEO and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were combined with Li in an EO unit configuration. + The molar ratio of the two components was 10:1, which were dissolved in acetonitrile solvent. Then, LiCl was added and stirred evenly to obtain an interface-stabilized slurry. The mass of LiCl accounted for 5 wt% of the total mass of the slurry. The slurry was then coated onto the other side of the dense inorganic electrolyte layer and finally vacuum dried at 80 °C for 24 hours to obtain a multi-level solid electrolyte. The thickness of the interface-stabilized layer after drying was 5 μm.

[0063] Example 2 A method for preparing a multi-level solid electrolyte includes the following preparation steps: Step 1: Prepare a high-pressure resistant interface layer: LiFSI and PVDF were dissolved in triethyl phosphate and stirred until homogeneous. The mass ratio of LiFSI, PVDF and triethyl phosphate was 1:1.5:40. Then, nano-AlF3 powder was added and ball-milled until homogeneous to obtain a high-pressure resistant slurry. The mass of nano-AlF3 powder accounted for 10 wt% of the total mass of the high-pressure resistant slurry. The high-pressure resistant slurry was cast into a film and dried to obtain a thin film with a thickness of 15 μm, namely the high-pressure resistant interface layer.

[0064] Step 2: After uniformly mixing PVDF and LPSC at a mass ratio of 9:1, press the mixture into a thin sheet under a cold pressing pressure of 10 MPa to obtain a dense inorganic electrolyte layer with a thickness of 50 μm. The ionic conductivity of the dense inorganic electrolyte layer is greater than 10. -4 S / cm.

[0065] Step 3: Align and bond the high-pressure resistant interface layer obtained in Step 1 and the inorganic electrolyte dense layer obtained in Step 2, and hot press them at 80℃ and 10 MPa for 5 minutes to obtain a composite membrane.

[0066] Step 4: Prepare the interface stabilizing layer: PEO and LiTFSI were combined with Li according to the EO unit. + The molar ratio of MgCl2 to MgCl2 is 10:1. The MgCl2 is dissolved in acetonitrile solvent, and then MgCl2 is added. After stirring evenly, an interface-stabilized slurry is obtained. The MgCl2 accounts for 5 wt% of the total mass of the slurry. The slurry is then coated on the other side of the inorganic electrolyte dense layer. Finally, it is vacuum dried at 80°C for 24 hours to obtain a multi-level solid electrolyte. The thickness of the interface-stabilized layer after drying is 5 μm.

[0067] Example 3 A method for preparing a multi-level solid electrolyte includes the following preparation steps: Step 1: Prepare a high-pressure resistant interface layer: LiTFSI and PAN were dissolved in triethyl phosphate and stirred until homogeneous. The mass ratio of LiTFSI, PAN and triethyl phosphate was 1:2:40. Then, nano LATP powder was added and ball-milled until homogeneous to obtain a high-pressure resistant slurry. The mass of nano LATP powder accounted for 15 wt% of the total mass of the high-pressure resistant slurry. The high-pressure resistant slurry was cast into a film and dried to obtain a film with a thickness of 15 μm, namely the high-pressure resistant interface layer. Step 2: After uniformly mixing PVDF and LPSC at a mass ratio of 9:1, press the mixture into a thin sheet under a cold pressing pressure of 10 MPa to obtain a dense inorganic electrolyte layer with a thickness of 50 μm. The ionic conductivity of the dense inorganic electrolyte layer is greater than 10. -4 S / cm.

[0068] Step 3: Align and bond the high-pressure resistant interface layer obtained in Step 1 and the inorganic electrolyte dense layer obtained in Step 2, and hot press them at 80℃ and 10 MPa for 5 minutes to obtain a composite membrane.

[0069] Step 4: Prepare the interface stabilizing layer: LiFSI and PVDF were dissolved in TEP and stirred until homogeneous. The mass ratio of LiFSI, PVDF and TEP was 1:1.5:40. Then AlCl3 was added and stirred until homogeneous to obtain an interface-stabilized slurry. The mass of AlCl3 accounted for 5 wt% of the total mass of the slurry. The slurry was then coated onto the other side of the dense inorganic electrolyte layer and finally vacuum dried at 80 °C for 24 hours to obtain a multi-level solid electrolyte. The thickness of the interface-stabilized layer after drying was 5 μm.

[0070] Example 4 A method for preparing a multi-level solid electrolyte includes the following preparation steps: Step 1: Prepare a high-pressure resistant interface layer: LiFSI and polypropylene carbonate (PPC) were dissolved in triethyl phosphate (TEP) at a mass ratio of 1:2:40. Then, LLZO powder was added and the mixture was ball-milled to obtain a high-pressure resistant slurry. The mass of nano-LLZO powder accounted for 15 wt% of the total mass of the high-pressure resistant slurry. The high-pressure resistant slurry was cast into a film and dried to obtain a 15 μm thick film, which is the high-pressure resistant interface layer. Step 2: Inorganic electrolyte dense layer, using commercially available LATP ceramic sheets, 50 μm thick, with an ionic conductivity greater than 10. -4 S / cm; Step 3: Align and bond the high-pressure resistant interface layer obtained in Step 1 and the inorganic electrolyte dense layer obtained in Step 2, and hot press them at 80℃ and 10 MPa for 5 minutes to obtain a composite membrane. Step 4: Prepare the interface stabilizing layer: LiFSI and PVDF were dissolved in TEP at a mass ratio of 1:1.5:40. SnCl2 was then added and stirred until homogeneous to obtain an interface-stabilized slurry. The mass of SnCl2 accounted for 5 wt% of the total slurry mass. The slurry was then coated onto the other side of the dense inorganic electrolyte layer and finally vacuum dried at 80 °C for 24 hours to obtain a multi-layered solid electrolyte. The thickness of the interface-stabilized layer after drying was 5 μm.

[0071] Comparative Example 1 LiFSI and PVDF were dissolved in TEP and stirred until homogeneous. The slurry was then cast into a film and dried to obtain a PVDF-LiFSI polymer electrolyte membrane. The mass ratio of LiFSI, PVDF, and TEP was the same as in Example 1, and the total thickness of the obtained PVDF-LiFSI polymer electrolyte membrane was the same as the total thickness of the multilayer solid electrolyte in Example 1.

[0072] Performance testing: The electrolytes from Examples 1-4 and the comparative examples were assembled into Li|electrolyte|Li symmetric cells and Li|electrolyte|NCM811 full cells, respectively, and their ionic conductivity, critical current density, and cycle performance were tested. In Examples 1-4, the high-voltage resistant interface layer of the electrolyte was located near the positive electrode, and the interface stabilizing layer was located near the negative electrode.

[0073] 1. Ionic conductivity testing method Using an electrochemical workstation, in a frequency range of 10 6 -10 -2AC impedance testing was performed on a Li|electrolyte|Li symmetric cell at room temperature (25±1℃) under conditions of Hz and a perturbation voltage of 10 mV. The bulk resistance R corresponding to the intersection of the high-frequency region and the real axis was read from the Nyquist plot. b (Unit: Ω). Calculate the ionic conductivity σ (unit: S·cm) according to the formula. -1 ): σ=L / (R) b ·A); where L is the electrolyte thickness (cm), and A is the electrode contact area (cm²). 2 ).

[0074] 2. Critical Current Density (CCD) Test Method A constant current charge-discharge test was performed on a Li|electrolyte|Li symmetric battery at room temperature using a Newway charge-discharge testing system. The initial current density was 0.1 mA / cm². 2 The deposition / stripping time was 1 h, followed by 5 cycles, and then at 0.1 mA / cm². 2 The current density is gradually increased until the battery short-circuites. The maximum current density before the short circuit occurs is the critical current density.

[0075] 3. Cyclic performance testing method (Li|electrolyte|NCM811 full cell) Positive electrode preparation: NCM811 active material, conductive carbon black and binder (PVDF) are mixed in a mass ratio of 90:5:5, coated on aluminum foil current collector, dried and then pressed and cut into sheets.

[0076] Battery assembly: In a glove box, use lithium metal as the negative electrode, the electrolyte to be tested as a separator / solid electrolyte, and NCM811 as the positive electrode to assemble a Li|electrolyte|NCM811 button or pouch full cell, and let it stand for 6-12 hours to age and stabilize the interface.

[0077] Using a battery testing system, constant current charge-discharge cycles were performed at a 1C rate in a constant temperature environment of 25℃. The charging cutoff voltage was set to 4.3 V and the discharging cutoff voltage was set to 2.8 V. The cycles were repeated 1000 times. The discharge capacity of the first cycle and the discharge capacity of the 1000th cycle were recorded. The capacity retention rate after 1000 cycles was calculated using the following formula.

[0078] Formula for calculating capacity retention: Capacity retention rate (%) = C 1000 / C 首圈放电容量 ×100%; where C 1000 This represents the discharge capacity after the 1000th cycle.

[0079] Table 1 Test Results From Table 1 and Figure 1-3 It can be seen that the embodiments of the present invention have higher ionic conductivity, critical current density and cycle capacity retention rate compared with Comparative Example 1; Figure 1 It can be seen that the present invention has a higher critical current density, indicating that the electrolyte of the present invention has superior anti-dendritic ability; from the present invention Figure 2 It can be seen that the present invention has a more stable overpotential and a longer cycle life; Figure 3 Example 1 shows the XPS pattern of an SEI formed on a lithium metal surface. The Cl 2p spectrum indicates that the SEI contains a large amount of LiCl, proving that the introduced nanoscale chloride inorganic filler can participate in the formation of the SEI.

[0080] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A multi-level solid electrolyte, characterized in that, The structure comprises, in sequence, an interface stabilizing layer, an inorganic electrolyte dense layer, and a high-voltage resistant interface layer, wherein the ionic conductivity of the inorganic electrolyte dense layer is greater than 10. -4 S / cm, the interface stabilizing layer comprises a first polymer and a chloride, the high-pressure resistant interface layer comprises a second polymer and a high-pressure resistant inorganic filler, and the oxidative decomposition voltage of the high-pressure resistant interface layer is greater than 4.5V.

2. The multi-level solid electrolyte according to claim 1, characterized in that, The chloride includes at least one of LiCl, MgCl2, SnCl2, AlCl3, InCl3, SiCl4, and SnCl4.

3. The multi-level solid electrolyte according to claim 1, characterized in that, The first polymer includes at least one of polyvinylidene fluoride-hexafluoropropylene and polyethylene oxide.

4. The multi-level solid electrolyte according to claim 1, characterized in that, The inorganic electrolyte dense layer includes at least one of garnet-type, sodium superionic conductor-type, sulfide-type, and halide-type inorganic solid electrolytes.

5. The multi-level solid electrolyte according to claim 1, characterized in that, The high-pressure resistant inorganic filler includes at least one of LLZO, LATP, MgF2, and AlF3.

6. The multi-level solid electrolyte according to claim 1, characterized in that, The second polymer includes at least one of polyvinylidene fluoride, polyacrylonitrile, polycarbonate, and polyphosphate.

7. The multi-level solid electrolyte according to any one of claims 1-6, characterized in that, The thickness of the interface stabilizing layer is 1-10 μm; And / or, the thickness of the inorganic electrolyte dense layer is 10-50 μm; And / or, the thickness of the high-pressure resistant interface layer is 5-20 μm.

8. A method for preparing a multi-level solid electrolyte, characterized in that, The preparation steps include the following: Step 1: Mix the second polymer and the high-pressure resistant inorganic filler with the solvent evenly to obtain a high-pressure resistant slurry. Coat the high-pressure resistant slurry onto an inert substrate and dry it to obtain a high-pressure resistant interface layer. Step 2: Hot-press the high-pressure resistant interface layer and the inorganic electrolyte dense layer together to obtain a composite film; Step 3: Dissolve the first polymer and chloride in a solvent to make a slurry. Coat the slurry onto the other surface of the inorganic electrolyte dense layer of the composite membrane. After drying, an interface stabilizing layer is formed on the surface of the inorganic electrolyte dense layer. Then, hot press to obtain a multi-level solid electrolyte.

9. An electrochemical device, characterized in that, The invention includes a positive electrode, a negative electrode, and a multi-level solid electrolyte disposed between the positive electrode and the negative electrode. The multi-level solid electrolyte is the multi-level solid electrolyte according to any one of claims 1-7 or the multi-level solid electrolyte prepared by the preparation method of claim 8. The interface stabilizing layer of the multi-level solid electrolyte is located on the side closer to the negative electrode, and the high-voltage resistant interface layer of the multi-level solid electrolyte is located on the side closer to the positive electrode.

10. An electronic device, characterized in that, Includes the electrochemical device as described in claim 9.

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